[Dr. DDS]

I bought 1Gb stick (gigaram memory) for my ibook and at first i thought it was ok. Then my ibook started being hot and th fans running all the time. I ran Apple Hardware Test and showed an error (2MEM/1/4IMM 1/J7). I changed the stick, ran AHT again and that time everything seemed just fine. But after a couple of weeks the same simptons started again and the computer freezed and opened a window saying "you have to reestart your computer holding down the power button" (or something like that, i dont't remerber the exactly words). When i reestarted it freezed again. I took out the RAM, ran AHT and everything was nice. So, o replaced the RAM again (it's the 3th) and in the first time it wasn't recognized and in the AHT showed error POST/0/2048. After some search i found that maybe it wasn't fit correctly, so i fit it wright, ran AHT and showed the same first error!!!
1) Is it possible that all 3 RAMs have problems?
2) Or maybe i have a problem in the place where the RAM fits in the logic board?

Here in Brazil one Apple Store told me to leave the ibook and the RAM for assistence, and another store said that maybe the memory had damaged the logic board because it wans't an apple certified memory.
3) Is it really possible? Afterall this brand has memory compatible with the ibook and the specs are correctly.

Thanks for any help,
regards